The bgl operon of E. coli K12 is cryptic in wild-type cells but can be activated by a number of mutations including insertions and point mutations within the operon, mutations that alter DNA gyrase activity, resulting reduced DNA supercoiling, and mutations in a gene termed bglY which act in an as yet undefined way. Our aim is to elucidate the mechanisms by which insertion sequences and other factors function to turn on the operon. We will determine (a) the role of DNA structure within the bgl regulatory region in operon expression, (b) how insertion positon is related to different levels of operon expression and (c) the role of sequences within Is1 and IS5 on operon expression and (d) if insertions and alterations in DNA supercoiling function to activate the operon in the same way. Once activated the bgl operon is subject to regulation at the level of transcription, becoming induced in the presence of beta- glucosides. This regulation may be related to operon activation, thus we intend to define the mechanism involved with emphasis on the role of the bglS and bglC gene products in this process.